1. Field of the Invention
The present invention generally relates to a multi-link engine. More specifically, the present invention relates to a link geometry for a multi-link engine.
2. Background Information
Engines have been developed in which a piston pin and a crank pin are connected by a plurality of links (such engines are hereinafter called multi-link engines). For example, a multi-link engine is disclosed in Japanese Laid-Open Patent Publication No. 2002-61501. A multi-link engine is provided with an upper link, a lower link and a control link. The upper link is connected to a piston, which moves reciprocally inside a cylinder by a piston pin. The lower link is rotatably attached to a crank pin of a crankshaft and connected to the upper link with an upper link pin. The control link is connected to the lower link with a control link pin for rocking about a rocking center pin.
An engine in which the piston and crankshaft are connected by single link (i.e., a connecting rod) is a common engine that is referred to hereinafter as a “single-link engine” in contrast to a multi-link engine. A distinctive characteristic of a multi-link engine is that it enables a long stroke to be obtained without increasing the top deck height (overall height), which is not possible in an engine having one link (i.e., connecting rod) connected between the piston and the crank shaft (an engine with one link is a normal engine but hereinafter will be referred to as a “single-link engine”). Technologies utilizing this characteristic are being researched, such as in Japanese Laid-Open Patent Publication No. 2006-183595.
In Japanese Laid-Open Patent Application No. 2006-183595, a sliding part of a piston (piston skirt) is formed with a minimal amount that is necessary. Additionally, the cylinder liner of the cylinder block is provided with a cutout such that a counterweight of the crankshaft and a link component can pass through the cutout of the cylinder liner. In this way, the position of a bottom end of the cylinder liner and the bottom dead center position of the piston can be lowered and a longer stroke can be achieved without increasing the overall height of the engine. Other related patent documents include Japanese Laid-Open Patent Publication No. 2001-227367 and Japanese Laid-Open Patent Publication No. 2005-147068
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved multi-link engine. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.